Parallel Plate Capacitor

A parallel plate capacitor is made of two circular disks. The distance between the disks is very small compared to their diameter. Initially, the disks are electrically neutral. After transferring 3.9x10^9 electrons from one disk to the other, the electric field strength in the space between the plates is 1.0x10^5 N/C. What is the diameter of the plates?

e = 1.6x10^-19C

2. Relevant equations

3. The attempt at a solution

I was able to calculate the charge on the plates by multiplying the number of electrons by their fundamental unit charge:

3.9x10^9 * 1.6^10-19C = 6.24x10^-10C

However I'm really lost as to what to do next. Any guidance would be much appreciated.